British APDS Problems

[rexford]

While this topic has been covered by many, including myself, in the past, an occasional reminder helps to keep APDS use in perpective.

British APDS was a good idea that didn't always work as planned. Army tests 2 and 3 on the Mycenius site at http://www.geocities.com/mycenius/ show that the rounds could have trouble hitting things.

The following analysis of firing tests against Tiger and Panther with 17 pdr APDS show how the penetration results could be far off the theoretical, which may be due to uneven shed of sabot petals leading to yaw and unstable trajectory:

The following analysis shows that many of the Panther glacis hits at Isigny, and against a captured Tiger tank, failed to penetrate when they should have. But the data also shows that 17 pdr APDS was capable of penetrating targets in accordance with the published curves on occasion.

The penetration figures in brackets show cases where 17 pdr APDS should have penetrated but didn't, and the failures appear to be due to more than random variations in penetration due to normal causes.

Isigny (fair hits only) vs Panther Glacis (55 glacis angle plus 2 degree ground for 57 degrees)

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200 yards, 1 pen on 3 hits, "271mm" penetration and 253mm armor resistance

300 yards, 1 failure, "266mm" penetration and 253mm resistance

400 yards, 1 pen on 6 hits, "262mm" penetration and 253mm resistance

600 yards, 2 failures, 253mm penetration and 253mm resistance

700 yards, 1 failure, 249mm penetration and 253mm resistance

Vs Captured Tiger (as function of impact velocity)

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3511 fps, 1 failure, 82mm/50 degree armor and "108mm"/50 degree penetration

3131 fps, 1 pen, 82mm/50 degree armor and 91mm/50 degree penetration

3437 fps, 1 failure, 102mm/48 degree armor and "115mm"/48 degree penetration

3215 fps, 1 failure, 102mm/48 degree armor and 105mm/48 degree penetration

3427 fps, 1 failure, 102mm/41 degree armor and "143mm"/41 degree penetration

3602 fps, 1 failure, 102mm/41 degree armor and "153mm"/41 degree penetration

Note how 82mm/50 degree armor case has success at 3131 fps and failure at 3511 fps, where failure ratio of penetration/armor is 1.32.

Also note that failures against 102mm/41 degree plate have penetration/armor ratio's of 1.40 and 1.50.

The above data suggests that a good share of the 17 pdr APDS rounds had greatly reduced effectiveness due to flight instability and yaw (and possible additional other factors).

The Tiger tank data is from Jentz' book on Tiger tanks and is analyzed on page 103 of our book. Jentz also presents penetration test data for 6 pdr APDS.

At Balleroy during summer 1944, two fair hits by 17 pdr APDS during Allied firing trials against the Panther glacis penetrated at 700 yards. The penetration/armor resistance ratio would be 249mm/226mm on level ground (55 degree impact angle) so the rounds penetrated according to theory (they worked at Balleroy).

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Lorrin

P.S. To be consistent with CMBB, the share of Panthers with deficient glacis armor should be less than 100%, and limited firing test data suggests that the quality of Panther armor against 17 pdr APDS should be about 95% instead of 85%.

This suggests that some type of dice roll system be used to determine how many effective APDS rounds will be allowed in a scenario, based on APDS problems and the Panther glacis resistance.

[Mr. Tittles]

I read that the US APDS round developed for the 76mm (too late for war in Europe) was, like the US 76mm HVAP, very accurate. This leads me to believe that the British 17 lbr was not designed or manufactured well.